(a) Field of the Invention
The present invention is related to a photo resist stripper composition, and more particularly to one with a designation of EZ Series solvent comprised of propylene glycol mono-methyl ether (PGME) or its derivatives, and cyclohexanone(ANONE) or its derivatives.
(b) Description of the Prior Art
In the manufacturing of microcircuit pattern to be used in the LCD circuit or semiconductor circuit, an insulation film or conduction metal film on the substrate is covered or coated with a photo resist comprised of epoxy, photoactive compound and solvent. The substrate is then oven dried at lower temperature to vaporize the solvent, selectively exposed to certain type of radiation including UV, electronic or X-ray, oven dried again at higher temperature, dipped in developer solution to create the expected pattern, and eroded to strip off residual photo resist on the insulation or the conduction metal film to complete the transfer of the micro-pattern to the surface of the substrate.
Whereas the distribution of the photo resist film on the edges of the substrate is not consistent when compared to that in the central area of the substrate, the unevenly distributed photo resist film or beads (formed by the lumps of the photo resist) in the chip must be removed to rinse the substrate. Currently, there are chemical and mechanical methods to remove the excessive photo resist or beads; however, either method apparently fails the expected results. Physical damage with losing of the material is taken for granted when the solidified film is mechanically stripped off. On the other hand, if the chemical method including rinse, clean or thinning with clean solvent is used, the photo resist stripper composition of the prior art usually contains Methyl isobutyl ketone (MIBK). MIBK though providing sufficient clean capacity, it is toxic to the human health and the environment, and its use is restricted in ISO 14000 Environmental Control Certification. Therefore, searching for a composition to substitute the MIBK is a must.
U.S. Pat. No. 4,983,490 discloses a type of photo resist stripper composition including from about 1 to about 10 of Propylene glycol mono-methyl ether (PGME) by weight and from about 1 to about 10 of Propylene glycol mono-methyl ether acetate (PGMEA) by weight. However, the clean results of the composition are found poor with certain types of photo resist and both of the solubility and vaporization rate are comparatively low. Furthermore, there are many types of photo resist compositions have been taught in U.S. Pat. Nos. 5,814,433; 5,849,467; 6,117,623, and 6,524,775. Additional to those compositions of mixed PGME and PGMEA, the photo resist stripper compositions (also known as ACS, Array clean solvent) popularly used in the trade also include the one-part n-Butyl Acetate (nBAc), or Isoamyl acetate (IAAc), or mixture of PGME, PGMEA and nBAc applied as coater cup rinse, glass substrate for edge bead remover (EBR), and tube clean in equipment.
Other than the price, many factors are taken into consideration in selecting a photo resist stripper composition that is harmless to human health, not affecting the social ecology, free of odors, fast and completely removing solidified or not yet matured photo resist film on the substrate, and giving excellent compatibility with various mixtures of photo resist without creating contamination or damage.